{"id":"UBUNTU-CVE-2025-59529","details":"Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In versions up to and including 0.9-rc2, the simple protocol server ignores the documented client limit and accepts unlimited connections, allowing for easy local DoS. Although `CLIENTS_MAX` is defined, `server_work()` unconditionally `accept()`s and `client_new()` always appends the new client and increments `n_clients`. There is no check against the limit. When client cannot be accepted as a result of maximal socket number of avahi-daemon, it logs unconditionally error per each connection. Unprivileged local users can exhaust daemon memory and file descriptors, causing a denial of service system-wide for mDNS/DNS-SD. Exhausting local file descriptors causes increased system load caused by logging errors of each of request. Overloading prevents glibc calls using nss-mdns plugins to resolve `*.local.` names and link-local addresses. As of time of publication, no known patched versions are available, but a candidate fix is available in pull request 808, and some workarounds are available. Simple clients are offered for nss-mdns package functionality. It is not possible to disable the unix socket `/run/avahi-daemon/socket`, but resolution requests received via DBus are not affected directly. Tools avahi-resolve, avahi-resolve-address and avahi-resolve-host-name are not affected, they use DBus interface. It is possible to change permissions of unix socket after avahi-daemon is started. But avahi-daemon does not provide any configuration for it. Additional access restrictions like SELinux can also prevent unwanted tools to access the socket and keep resolution working for trusted users.","modified":"2026-05-20T16:23:41.368056318Z","published":"2025-12-18T21:15:00Z","upstream":["CVE-2025-59529"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-59529"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-59529"},{"type":"REPORT","url":"https://github.com/avahi/avahi/security/advisories/GHSA-73wf-3xmj-x82q"},{"type":"REPORT","url":"https://zeropath.com/blog/avahi-simple-protocol-server-dos-cve-2025-59529"}],"affected":[{"package":{"name":"avahi","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/avahi?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.31-2ubuntu4","0.6.31-2ubuntu5","0.6.31-3ubuntu1","0.6.31-4ubuntu1","0.6.31-4ubuntu1.1","0.6.31-4ubuntu1.2","0.6.31-4ubuntu1.3","0.6.31-4ubuntu1.3+esm1","0.6.31-4ubuntu1.3+esm2","0.6.31-4ubuntu1.3+esm3","0.6.31-4ubuntu1.3+esm4","0.6.31-4ubuntu1.3+esm5"],"ecosystem_specific":{"binaries":[{"binary_name":"avahi-autoipd","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_name":"avahi-daemon","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_version":"0.6.31-4ubuntu1.3+esm5","binary_name":"avahi-discover"},{"binary_name":"avahi-dnsconfd","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_version":"0.6.31-4ubuntu1.3+esm5","binary_name":"avahi-ui-utils"},{"binary_name":"avahi-utils","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_name":"libavahi-client3","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_name":"libavahi-common-data","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_name":"libavahi-common3","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_version":"0.6.31-4ubuntu1.3+esm5","binary_name":"libavahi-compat-libdnssd1"},{"binary_name":"libavahi-core7","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_name":"libavahi-glib1","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_name":"libavahi-gobject0","binary_version":"0.6.31-4ubuntu1.3+esm5"},{"binary_version":"0.6.31-4ubuntu1.3+esm5","binary_name":"libavahi-qt4-1"},{"binary_version":"0.6.31-4ubuntu1.3+esm5","binary_name":"libavahi-ui-gtk3-0"},{"binary_version":"0.6.31-4ubuntu1.3+esm5","binary_name":"libavahi-ui0"},{"binary_version":"0.6.31-4ubuntu1.3+esm5","binary_name":"python-avahi"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-59529.json"}},{"package":{"name":"avahi","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/avahi?arch=source&distro=esm-infra-legacy%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.31-4ubuntu4","0.6.32~rc+dfsg-1ubuntu2","0.6.32~rc+dfsg-1ubuntu2.1","0.6.32~rc+dfsg-1ubuntu2.2","0.6.32~rc+dfsg-1ubuntu2.3","0.6.32~rc+dfsg-1ubuntu2.3+esm1","0.6.32~rc+dfsg-1ubuntu2.3+esm2","0.6.32~rc+dfsg-1ubuntu2.3+esm3","0.6.32~rc+dfsg-1ubuntu2.3+esm4","0.6.32~rc+dfsg-1ubuntu2.3+esm5"],"ecosystem_specific":{"binaries":[{"binary_name":"avahi-autoipd","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"avahi-daemon","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"avahi-discover","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"avahi-dnsconfd","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5","binary_name":"avahi-ui-utils"},{"binary_name":"avahi-utils","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"libavahi-client3","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"libavahi-common-data","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"libavahi-common3","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"libavahi-compat-libdnssd1","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"libavahi-core7","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"libavahi-glib1","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"libavahi-gobject0","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5","binary_name":"libavahi-qt4-1"},{"binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5","binary_name":"libavahi-ui-gtk3-0"},{"binary_name":"libavahi-ui0","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"},{"binary_name":"python-avahi","binary_version":"0.6.32~rc+dfsg-1ubuntu2.3+esm5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-59529.json"}},{"package":{"name":"avahi","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/avahi?arch=source&distro=esm-infra%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.32-1ubuntu1","0.7-3ubuntu1","0.7-3ubuntu2","0.7-3.1ubuntu1","0.7-3.1ubuntu1.1","0.7-3.1ubuntu1.2","0.7-3.1ubuntu1.3","0.7-3.1ubuntu1.3+esm1","0.7-3.1ubuntu1.3+esm2","0.7-3.1ubuntu1.3+esm3","0.7-3.1ubuntu1.3+esm4"],"ecosystem_specific":{"binaries":[{"binary_versi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